﻿#pragma once
template<class K, class V>

struct AVLTreeNode

{
	// 需要parent指针，后续更新平衡因⼦可以看到 
	pair<K, V> _kv;
	AVLTreeNode<K, V>* _left;
	AVLTreeNode<K, V>* _right;
	AVLTreeNode<K, V>* _parent;
	int _bf; // balance factor

	AVLTreeNode(const pair<K, V>& kv)
		:_kv(kv)
		, _left(nullptr)
		, _right(nullptr)
		, _parent(nullptr)
		, _bf(0)
	{
	}
};


template<class K, class V>

class AVLTree

{
	typedef AVLTreeNode<K, V> Node;

public:
	bool Insert(const pair<K,V> kv)
	{
		if (_root == nullptr)
		{
			_root = new Node(kv);
			return true;
		}
		Node* parent = nullptr;
		Node* cur = _root;
		while (cur)
		{
			if (cur->_kv.first < kv.first)
			{
				parent = cur;
				cur = cur->_right;
			}
			else if (cur->_kv.first > kv.first)
			{
				parent = cur;
				cur = cur->_left;
			}
			else

			{
				return false;
			}
		}
		cur = new Node(kv);
		if (parent->_kv.first < kv.first)
		{
			parent->_right = cur;
		}
		else

		{
			parent->_left = cur;
		}

		cur->_parent = parent;
		while (parent)
		{
			if (cur == parent->_right)
			{
				parent->_bf++;
			}
			else if (cur == parent->_left)
			{
				parent->_bf--;
			}
			if (parent->_bf == 0)
			{
				break;
			}
			else if (parent->_bf == 1 || parent->_bf == -1)
			{
				cur == parent;
				parent = parent->_parent;
			}
			else if (parent->_bf == 2 || parent->_bf == -2)
			{

				if (parent->_bf == -2 && cur->_bf == -1)
				{
					RotateR(parent);
				}
				if (parent->_bf == 2 && cur->_bf == 1)
				{
					RotateL(parent);
				}
				break;
			}
			else
			{
				assert(false);
			}
		}
		return true;
	}

private:
	void RotateR(Node* parent)
	{
		Node* subL = parent->_left;
		Node* subLR = subL->_right;

		parent->_left = subLR;
		if(subLR)
			subLR->_parent = parent;
		Node* ppnode = parent->_parent;
		subL->_right = parent;
		parent->_parent = subL;
		if (parent == _root)
		{
			_root = subL;
			subL->_parent = nullptr;
		}
		else
		{
			if (ppnode->_left == parent)
			{
				ppnode->_left = subL;
			}
			else
			{
				ppnode->_right = subL;
			}
			subL->_parent = ppnode;
		}
		subL->_bf = parent->_bf = 0;
	}
	void RotateL(Node* parent)
	{
		Node* subR = parent->_right;
		Node* subRL = subR->_left;

		parent->_right = subRL;
		if (subRL)
			subRL->_parent = parent;
		Node* ppnode = parent->_parent;
		subR->_left = parent;
		parent->_parent = subR;
		if (parent == _root)
		{
			_root = subR;
			subR->_parent = nullptr;
		}
		else
		{
			if (ppnode->_left == parent)
			{
				ppnode->_left = subR;
			}
			else
			{
				ppnode->_right = subR;
			}
			subR->_parent = ppnode;
		}
		subR->_bf = parent->_bf = 0;
	}
	Node * _root = nullptr;
};
